Problem 153

Question

If \(A=\left[\begin{array}{ccc}1 & -5 & 7 \\ 0 & 7 & 9 \\ 11 & 8 & 9\end{array}\right]\), then find the trace of matrix \(A\)

Step-by-Step Solution

Verified
Answer
The trace of matrix A is 17.
1Step 1: Identify the elements on the main diagonal of the matrix
In the given matrix A, the elements on the main diagonal are 1, 7, and 9.
2Step 2: Add up the elements on the main diagonal
Add these elements together to get the trace of the matrix. So, the trace of matrix A is \(1 + 7 + 9 = 17\).

Key Concepts

Understanding MatricesIdentifying Diagonal ElementsBasics of Matrix Operations
Understanding Matrices
A matrix is a rectangular arrangement of numbers, symbols, or expressions, arranged in rows and columns. A simple way to visualize a matrix is like a small table that organizes numbers neatly. The overall size or shape of a matrix is described as "m x n," where "m" is the number of rows, and "n" is the number of columns.

An example matrix might look like this:
  • Matrix A, a 3x3 matrix:
\[A = \begin{pmatrix} 1 & -5 & 7 \ 0 & 7 & 9 \ 11 & 8 & 9 \end{pmatrix}\]Each number in the matrix is an element. In matrix A, the element in the first row and first column is 1. Matrices are used across different fields, including computer graphics, statistics, and engineering.

Understanding matrices is fundamental because they form the foundation for various operations and calculations in linear algebra, such as finding the trace of a matrix.
Identifying Diagonal Elements
Diagonal elements are specific numbers in a square matrix (where the number of rows equals the number of columns) that form a diagonal line from the upper left to the bottom right corner. This diagonal is often referred to as the "main diagonal."
  • In matrix A, the main diagonal consists of the numbers 1, 7, and 9.
When looking at the diagonal elements, you start with the top-left element and continue towards the bottom-right, counting only those elements that fall in a straight line between them.

Recognizing diagonal elements is crucial for certain calculations, such as determining the trace of a matrix, which is simply the sum of these diagonal values.
Basics of Matrix Operations
Matrix operations are actions you can perform on matrices, such as addition, subtraction, and multiplication. These operations are essential for solving mathematical problems involving matrices.

One specific matrix operation is calculating the trace. The trace of a square matrix is the sum of all its diagonal elements. It is a straightforward calculation involving adding numbers:
  • For matrix A, trace is calculated as \(1 + 7 + 9 = 17\)
Matrix operations enable us to solve complex problems efficiently, making them invaluable tools in fields like physics, economics, and data science.

Understanding these operations also helps when exploring more advanced topics like determinants and eigenvalues, which build upon basic matrix concepts.